The orthogonal frequency division multiplexing (OFDM) scheme, which is one of data transmission methods in the wireless communication system, is actively applied to the mobile communication field because of its excellent characteristics.
In general, the OFDM method modulates respective symbol sequences into corresponding subcarriers in the frequency domain and multiplexes them. As the number of subcarriers is increased, the peak-to-average power ratio (PAPR) is also increased. That is, the OFDM method has a characteristic of a high PAPR compared to other types of transmission methods, which is known as the major disadvantage of the OFDM method.
Further, the high PAPR is more disadvantageous in uplink rather than downlink since the high PAPR increases the price of the mobile terminal and reduces the uplink coverage.
To solve the problems, the single carrier frequency division multiple access (SC-FDMA) is proposed, in which an information symbol sequence is digital Fourier transform (DFT) spread, OFDM modulated, and transmitted. In detail, a transmitted signal has a low PAPR in a like manner of the single frequency modulation signal according to an appropriate relationship between the DFT of the preprocessing and the inverse fast Fourier transform (IFFT) of the OFDM modulation process.
However, the low PAPR characteristic of the SC-FDMA transmission signal is to be maintained during the pilot transmission interval as well as during the data transmission interval, and hence the SC-FDMA type of pilot channel is required to consider the low pilot overhead and the low PAPR maintenance in the case of designing the SC-FDMA type pilot channel. That is, in the case of time-division multiplexing the pilot channel and a data channel, it is easy to maintain the low PAPR of the pilot transmission signal, and in the case of the frequency and code division multiplexing, the data signal and the pilot signal are superimposed in the time domain to thus increase the PAPR.
Further, a related prior art is a pilot channel forming method which maintains the low PAPR of the SC-FDMA signal and simultaneously controls the pilot overhead to be not excessive and which is applicable in common to the localized frequency division multiple access (L-FDMA) and the distributed frequency division multiple access (D-FDMA).
However, the pilot channel forming method increases the frequency resolution of the pilot signal compared to the data signal to thus decrease the channel estimation performance.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.